U.S. patent application number 17/289914 was filed with the patent office on 2022-01-06 for transferring printing fluid to a substrate.
This patent application is currently assigned to Hewlett-Packard Development Company, L.P.. The applicant listed for this patent is Hewlett-Packard Development Company, L.P.. Invention is credited to Ehud EYAL, Eric NELSON, Nadav SHALEM.
Application Number | 20220004115 17/289914 |
Document ID | / |
Family ID | 1000005896871 |
Filed Date | 2022-01-06 |
United States Patent
Application |
20220004115 |
Kind Code |
A1 |
EYAL; Ehud ; et al. |
January 6, 2022 |
TRANSFERRING PRINTING FLUID TO A SUBSTRATE
Abstract
Some examples relate to printing apparatuses and methods. In an
example, a roller transfers printing fluid to a substrate. In some
examples an electrically grounded roller is positioned proximate
the electrically charged roller and guides the substrate. In some
examples, the roller is an electrically charged roller. In some
examples an electric field is applied and its strength is varied
based on a dielectric coefficient of the substrate and/or a
thickness of the substrate.
Inventors: |
EYAL; Ehud; (Ness Ziona,
IL) ; NELSON; Eric; (Boise, ID) ; SHALEM;
Nadav; (Ness Ziona, IL) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Hewlett-Packard Development Company, L.P. |
Spring |
TX |
US |
|
|
Assignee: |
Hewlett-Packard Development
Company, L.P.
Spring
TX
|
Family ID: |
1000005896871 |
Appl. No.: |
17/289914 |
Filed: |
December 12, 2018 |
PCT Filed: |
December 12, 2018 |
PCT NO: |
PCT/US2018/065280 |
371 Date: |
April 29, 2021 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
G03G 15/065 20130101;
G03G 15/10 20130101 |
International
Class: |
G03G 15/06 20060101
G03G015/06; G03G 15/10 20060101 G03G015/10 |
Claims
1. An apparatus comprising: a first roller to transfer printing
fluid to a substrate, the first roller being connected to a source
of electrical potential; and an electrically grounded roller to
guide a substrate, wherein the electrically grounded roller is
positioned proximate the electrically charged roller.
2. An apparatus according to claim 1, wherein the apparatus is to
advance the substrate in between the first roller and the
electrically grounded roller.
3. An apparatus according to claim 1 wherein the first roller is
connected to a source of direct current, the apparatus further
comprising a controller to vary the strength of direct current in
proportion to a dielectric coefficient of the substrate and/or a
thickness of the substrate.
4. An apparatus according to claim 1 wherein the first roller is
connected to a source of alternating current, the apparatus further
comprising a controller to vary the strength and/or the frequency
of alternating current.
5. An apparatus according to claim 1 wherein the first roller is
connected to a source of DC such that the electrically charged
roller is held at a negative potential.
6. A method comprising: receiving printing fluid at a developer
roller; applying an electric field in the region of the developer
roller; advancing a substrate proximate the developer roller; and
varying the strength of the electric field based on a dielectric
coefficient of the substrate and/or a thickness of the
substrate.
7. A method according to claim 6, wherein advancing a substrate
proximate the developer roller comprises advancing the substrate
between the developer roller and an electrically grounded
roller.
8. A method according to claim 6 wherein applying an electric field
in the region of the developer roller comprises supplying a current
to the developer roller to create a potential difference between
the developer roller and a region through the substrate.
9. A method according to claim 8 wherein advancing the substrate
proximate the developer roller comprises advancing the substrate in
between the developer roller and a guide roller, wherein applying
the electric field in the region of the develop roller comprises:
supplying a current to the developer roller and connecting the
guide roller to a ground to thereby create a potential difference
between the developer roller and the guide roller.
10. A method according to claim 8 wherein advancing the substrate
proximate the developer roller comprises advancing the substrate in
between the developer roller and a guide roller, wherein applying
the electric field in the region of the develop roller comprises:
supplying a first current to the developer roller and a second
current to the guide roller to create a potential difference
between the developer roller and the guide roller, the first and
second currents being different.
11. An apparatus comprising a developer roller to receive printing
fluid and to transfer a portion of the printing fluid to a print
media; an electrically grounded roller to direct a print media in
between the developer roller and the electrically grounded roller;
and a controller to apply an electric field between the developer
roller and the guide roller.
12. An apparatus according to claim 11, wherein the controller is
to vary the strength of the electric field based on a dielectric
coefficient and/or a thickness of the print media.
13. An apparatus according to claim 11, wherein the apparatus
further comprises an engage mechanism to move one of the developer
roller and the electrically grounded roller to a position proximate
to the other.
14. An apparatus according to claim 11, wherein the controller is
to supply current to the developer roller to create the electric
field between the developer roller and the guide roller.
15. An apparatus according to claim 14, wherein the controller is
to supply current to the developer roller to maintain the developer
roller at a negative potential.
Description
BACKGROUND
[0001] In some printing systems, printing fluid such as an ink is
transferred from an inking roller to an advancing substrate.
BRIEF DESCRIPTION OF DRAWINGS
[0002] Examples will now be described, by way of non-limiting
example, with reference to the accompanying drawings, in which:
[0003] FIG. 1 is a simplified schematic of an example of
apparatus;
[0004] FIG. 2 is a flowchart of an example of a method;
[0005] FIG. 3 is a simplified schematic of an example of
apparatus;
[0006] FIG. 4 is a flowchart of an example of a method; and
[0007] FIG. 5 is an example of a machine readable medium in
association with a processor.
DETAILED DESCRIPTION
[0008] Some printing systems that transfer a printing fluid, such
as ink (e.g. conductive ink), to a substrate comprise a number of
rollers that, through their rotation transfer ink to a substrate
advancing through the printing system. For example, a first roller
may collect ink from a reservoir and, via rotational engagement
with a second roller (such as a photoreceptor), transfer a portion
of that ink to the second roller (and a latent image formed
thereon). The second roller may then transfer the ink from the
inked latent image to a substrate advancing between the second
roller and a third roller. These example printing systems may
function to print a specific image (e.g. the latent image) onto a
particular substrate.
[0009] Some examples herein relate to printing systems and methods
that are capable of transferring ink to a substrate without an
intermediate member (e.g. a roller) in between two rollers (such as
a guide roller and a roller to transfer ink to the substrate).
[0010] FIG. 1 shows an example apparatus 100. The apparatus 100 may
be an apparatus to deposit or transfer ink to a substrate. In one
example the apparatus 100 may be a printing apparatus.
[0011] The apparatus 100 comprises a first roller 102. The first
roller 102 is to transfer printing fluid (not shown in FIG. 1),
such as ink, to a substrate 104 and is connected to a source 112 of
electrical potential. For example, an printing fluid supply
apparatus, or applicator, may engage the first roller 102 so as to
deposit printing fluid thereon. In one example, an printing fluid
applicator is to transport a supply of printing fluid to the
surface of the first roller 102, for example the printing fluid
applicator may be a roller in contact with a printing fluid
reservoir, wherein revolutions of the printing fluid applicator
roller may cause printing fluid from the reservoir to be deposited
onto its surface, and the printing fluid applicator roller may, via
contact between the ink applicator roller and the first roller 102,
transfer its ink to the first roller 102. In some examples the
first roller 102 may be a binary ink developer.
[0012] The apparatus 100 comprises an electrically grounded roller
106. The electrically grounded roller 106 is positioned proximate
to the electrically charged roller 104. During a print or inking
operation, the apparatus 100 may be to advance the substrate 104
between the grounded roller 106 and the first roller 102. The first
and grounded rollers 102, 106 may be rotatable. For example, the
first and grounded rollers 102, 106 are rotatable so as to guide
(or, in some examples, advance) a substrate 104 through the
apparatus 100. In other examples, a separate (not shown) drive unit
may be to advance the substrate 104 through the apparatus 100 and
in between the two rollers 102, 106.
[0013] The electrically grounded roller 106 is connected to the
ground 110. That is, the potential of the electrically grounded
roller 106 is maintained at 0V. For example, the electrically
grounded roller 106 may comprise an end surface which rotates,
along with the rest of the grounded roller 106, about a central
grounded roller axis. A rotatable coupling such as bearing, bushing
or brush (e.g. a brush spring-biased into contact with the
electrically grounded roller 106) may be connected to the ground
110 and, via its engagement with the electrically grounded roller
106, may maintain the grounded roller 106 at a potential of 0V.
[0014] In one example the grounded roller 106 may comprise a
conductor. For example, an outer surface of the grounded roller 106
may comprise a conductor. The conductor may comprise a metal. In
one example the grounded roller may comprise a metallic outer
surface. In examples that utilise a rotatable coupling, a metallic
outer surface, or metallic part of the grounded roller 106, may be
in contact with the rotatable coupling so as to connect the
grounded roller 106 to the ground 110.
[0015] In the example of FIG. 1 the first roller 102 is maintained
at a negative potential. For example, the first roller 102 is
connected to a source of direct current (DC) and a controller 108
is to control the current supplied to the electrically charged
roller 102, e.g. to maintain a negative potential. In this way the
first roller 102 may be referred to as an electrically charged
roller 102 since, as explained in further detail below, charge
accumulation as a result of the electrical connection to the source
112 may result in a potential difference between the two rollers
102, 106. The charged roller may comprise a semiconducting
material.
[0016] For example, the charged roller 102 may be in contact with a
rotatable coupling such as a bearing, bushing or brush, and the
rotatable coupling may be in contact with a source of DC (e.g. a
negative terminal thereof, such as a negative electrode). For
example, the DC source may supply current to the charged roller 102
via a rotatable coupling comprising a conductor. The conductor may
comprise a metal. For example, a bearing comprising a metallic
bearing housing may be connected to a conductor (e.g. copper wire
etc.) connected to a DC source. A rotatable bearing element within
the bearing housing may then transfer the current from the
conductor, through the bearing housing, to part of the charged
roller 102 to supply the current to the charged roller 102, e.g. to
maintain it at a negative potential. In one example, the charged
roller 102 may be connected to a source of alternating current
(AC), and the controller 108 may be to vary the strength and/or
frequency of the AC. In this example, the apparatus 100 may
comprise a rectifier to convert the AC to DC.
[0017] In one example, (e.g. in use) the charged roller 102 is
connected to a source of DC, e.g. under the control of the
controller 108, so as to supply current to the charged roller 102.
In another example (as above), the charged roller 102 may be
connected to source of AC. The current source and charged roller
102 therefore form an open circuit as charge from the current
source accumulates on the charged roller 102. For example, current
supplied to the charged roller 102 may cause a region of negative
charge to accumulate on the surface of the charged roller 102
(positive charge may accumulate toward the centre of the charged
roller 102). As a result, a potential difference, or voltage, is
created across the gap between the charged roller 102 and the
grounded roller 106. An electric field may therefore form between
the charged roller 102 and the grounded roller 106. The air between
the surfaces of the charged roller 102 and grounded roller 105 may
develop an electrical conductivity. The apparatus 100 (e.g. under
the control of a controller, e.g. controller 108) may advance the
substrate 104 in between the charged and grounded rollers 102, 106,
and printing fluid may be transferred to the charged roller 102,
e.g. as described above. As printing fluid is transferred to the
charged roller 102, and the charged roller 102 rotates, the
printing fluid on the surface of the charged roller 102 will be
rotated into proximity with the grounded roller 106, and rotated
into proximity with the substrate 104 advancing in between the two
rollers 102, 106. Due to the potential difference (electric field)
in between the two rollers 102, 106, printing fluid on the surface
of the charged roller 102 may be caused to migrate toward the
grounded roller 102 whereupon it will be deposited onto the surface
of the substrate 104 advancing in between. The apparatus 100
therefore forms an open circuit in which accumulated charge on the
charged roller 102 is unable to migrate to the grounded roller to
complete the circuit, thereby causing a potential difference
therebetween, the potential difference and resulting electric field
facilitating the transfer of ink toward the ground, and therefore
toward the substrate. The substrate 104 thereby forms an effective
resistor in this open circuit. Therefore, the apparatus 100
deposits ink onto the surface of the substrate 104.
[0018] The printing fluid may therefore comprise conductive ink and
may, when placed in an electric field, flow towards a higher
potential. For example the ink may comprise charged particles and
an applied electric field may cause the charged particles to move
towards a higher potential, for example the ink may comprise
negatively charged particles). In the example of FIG. 1, the
charged roller 102 is maintained at a negative potential (in one
example a constant negative potential) and therefore the ink, due
to the potential difference between the two rollers 102, 106
migrates toward the grounded roller 102, being the higher potential
at 0V in this example.
[0019] In one example, the controller 108 is to vary the strength
of the DC in proportion to the dielectric coefficient of the
substrate. For example, substrates of different composition (e.g.
comprising plastic or paper) or of different thickness may comprise
different dielectric coefficients. Generally speaking, the higher
the dielectric coefficient the higher the potential difference
between the grounded 106 and charged 102 roller needs to be for ink
to successfully migrate from the charged roller 102 to the grounded
roller 106 and therefore to be deposited onto the substrate 104. In
some examples the thicker the substrate 104 the higher the
dielectric coefficient. Accordingly, in some examples the
controller 108 may be to measure the thickness of the substrate 104
and adjust the current supplied to the charged roller 102 based on
the measured thickness. In other examples, the controller 108 may
comprise a memory, and the dielectric coefficient of a particular
substrate 104 may be entered into the controller 108 which (e.g.
via a look-up table) may associate a particular current value to
supply to the charged roller 102 so as to ensure ink migration
toward the grounded roller 102 for that substrate 104.
[0020] The potential of the charged roller 102 and grounded roller
106 may therefore be relative to the dielectric coefficient of the
substrate. In one example the controller 108 may be to maintain the
charged roller 102 at -400V, and, in response to a change in
dielectric coefficient of the substrate (which may result from an
increased thickness of the substrate), the controller 108 may be to
maintain the charged roller at -1000V. In some examples, the first
roller 102 may be connected to a source of electrical potential
such that the potential is non-uniform along a dimension (e.g. a
length) of the first roller.
[0021] The apparatus 100 may be to substantially cover the
substrate 104 with printing fluid. For example, the apparatus 100
may be to print a background on a substrate 104. For example, if
the electrically charged roller 102 is to receive red ink then, in
use, the apparatus 100 may be to substantially cover the substrate
104 with red ink, thereby printing a red background onto the
substrate. In this way the apparatus 100 may be to "flood" the
substrate 104 with ink. For example, the substrate 104 may be a
paper or plastic substrate intended for use with product packaging
and the apparatus 100 may be to print a background colour onto the
substrate.
[0022] FIG. 2 shows an example method 200. The method 200 may be a
method of printing (or transferring or depositing) printing fluid
to a substrate. The method 200 may be a method of printing a
substrate. The method 200 may be a method of substantially flooding
a substrate with printing fluid.
[0023] The method 200 comprises, at block 202, receiving printing
fluid at a developer roller. The developer roller may be a binary
ink developer. Block 202 may comprise engaging a developer roller
with an ink applicator (e.g. a roller) which is in contact with an
printing fluid reservoir so as to transfer printing fluid from the
reservoir to the developer roller. In one example, the developer
roller may be in contact with the printing fluid reservoir. In one
example rotatable contact between the printing fluid applicator
roller and the develop roller may facilitate the printing fluid
transfer and therefore in one example block 202 of the method 200
may comprise engaging the printing fluid applicator roller to
transfer printing fluid from a printing fluid reservoir to the
developer roller.
[0024] The method 200 comprises, at block 204, applying an electric
field in the region of the developer roller. The method 200
comprises, at block 206, advancing a substrate proximate the
developer roller. For example, block 206 may comprise advancing a
substrate proximate the developer roller and a second roller, Block
206 may comprise advancing a substrate in between the developer
roller and a second roller. The second roller may be a grounded
roller.
[0025] In one example applying the electric field, at block 204,
comprises controlling two electrodes (one positive, one negative)
in a region of the developer roller. In this example, the negative
electrode may be proximate the developer roller and the positive
electrode may be proximate the second roller. This creates an
electric field and potential difference between the developer
roller and a second roller (e.g. advancing the substrate) which
causes the ink at the developer roller to migrate toward the second
roller (at higher potential) whereupon it will be deposited on the
advancing substrate. In another example, applying an electric
field, at block 204, may comprise applying a current through the
developer roller. For example, current may be supplied to the
developer roller so that it is maintained at a negative potential.
In another example, current may be supplied to the developer roller
so that it is maintained at a negative potential and a second
roller guiding the substrate may be maintained at a negative
potential (but less negative, and therefore more positive, than the
negative potential of the developer roller) or may be maintained at
0V (e.g. grounded). In another example, current may be supplied to
the developer roller so that it is maintained at a positive
potential and a second roller guiding the substrate may be
maintained at a positive potential (but a higher positive potential
than the developer roller), ink in this example therefore migrating
toward the second roller (the more positive potential) to be
deposited on the advancing substrate. The second roller may be a
guide roller to guide the substrate or a drive roller to advance
the substrate, Thus, in one example, block 206 comprises advancing
the substrate between the developer roller and an electrically
grounded roller.
[0026] The method 200 comprises, at block 208, varying the strength
of the electric field based on a dielectric coefficient, and/or a
thickness, of the substrate. As the dielectric coefficient (and its
thickness) of the substrate may affect the printing fluid transfer
to the substrate (e.g. the percentage of printing fluid that is
transferred from the developer roller onto the substrate), in some
examples block 208 may comprise measuring a thickness of the
substrate 104 to infer the dielectric coefficient and varying the
electric field based on the measurement. For example, block 208 may
comprise consulting a look-up table, the look-up table being able
to associate a current to a dielectric coefficient (or a thickness
of the substrate), and the current may be adjusted to that value.
In another example, the look-up table may associate a field
strength to a dielectric coefficient.
[0027] In one example, block 204 comprises supplying a current to
the developer roller so as to create a potential difference between
the developer roller and the substrate or a region proximal
thereto. As above, this will facilitate printing fluid migration
towards and onto the substrate. In this example, block 208
comprises varying the current supplied to the develop roller based
on the dielectric coefficient of the substrate.
[0028] In one example, block 206 comprises advancing the substrate
in between the developer roller and a second, guide, roller, and
block 204 comprises supplying a current to the developer roller and
connecting the guide roller to the ground. In this example, block
206 comprises supplying current to the developer roller so that it
is at a negative potential. In this example, a potential difference
is created between the developer roller and the guide roller
causing the printing fluid to migrate toward the higher potential
(the ground in this case). In this example block 208 comprises
varying the current level supplied to the developer roller in
proportion to the dielectric coefficient of the substrate. In
another example, block 204 comprises supplying a first current to
the developer roller and a second current to the guide roller. The
first current may be to maintain the developer roller at a lower
potential than the guide roller so that the guide roller is at a
higher potential, thereby ensuring that ink migration is from the
developer roller toward to the guide roller (migrating in being
deposited on the substrate advancing therebetween). In this example
block 208 comprises varying the current supplied to one, or both,
of the developer roller and the guide roller. For example, to
increase the potential difference between the rollers, e.g. varying
the electric field, block 208 may comprise increasing the current
to the guide roller and/or decreasing the current to the developer
roller.
[0029] In one example, block 204 may comprise supplying a current
to maintain the developer roller at a potential of -400V and, block
208 may comprise supplying a current to maintain the developer
roller at -1000V, e.g. in response to a changing dielectric
coefficient of the substrate. In another example, block 204 may
comprise supplying a current to maintain the developer roller at
+40V and supplying a current to maintain the guide roller at
+250V.
[0030] In one example, applying the electric field at block 204
comprises supplying two electrodes with a current or a source of
electrical potential. For example, in one example block 204
comprises supplying a electrical potential to two conductive plates
such that they are at a different electrical potential to thereby
create a voltage therebetween.
[0031] FIG. 3 shows an example apparatus 300. The apparatus 300 may
be an apparatus to deposit or transfer printing fluid to a
substrate. In one example the apparatus 300 may be a printing
apparatus.
[0032] The apparatus 300 comprises a developer roller 302. The
developer roller 302 is to receive printing fluid (not shown in
FIG. 3) and to transfer a portion of the printing fluid to a print
target, such as a print media 304. For example, a printing fluid
supply apparatus, or applicator, may engage the developer roller
302 so as to deposit printing fluid thereon. In one example, an ink
applicator is to transport a supply of printing fluid to the
surface of the developer roller 302, for example, the printing
fluid applicator may be a roller in contact with a printing fluid
reservoir, wherein revolutions of the printing fluid applicator
roller may cause printing fluid from the reservoir to be deposited
on to the surface thereon, and the printing fluid applicator roller
may, via contact between the printing fluid applicator roller and
the developer roller 302, transfer printing fluid to the developer
roller 302. In some examples the developer roller 302 may be a
binary ink developer.
[0033] The apparatus 300 comprises an electrically grounded roller
306. The electrically grounded roller 306 is to direct a print
media 304 between the developer roller 302 and the grounded roller
302. During a print operation, the apparatus 300 is to advance the
print media 304 between the grounded roller 306 and the developer
roller 302. The developer and grounded rollers 302, 306 may be
rotatable. For example, the developer and grounded rollers 302, 306
may be rotatable so as to guide or advance a print media 304
through the apparatus 300. In other examples, a (not shown) drive
unit may be to advance the print media 304 through the apparatus
300 and in between the two rollers 302, 306.
[0034] The electrically grounded roller 306 is connected to the
ground 310. That is, the potential of the electrically grounded
roller 306 is maintained at 0V. For example, the electrically
grounded roller 306 may comprise an end surface which rotates,
along with the rest of the grounded roller 306, about a central
grounded roller axis. A rotatable coupling such as bearing, bushing
or brush (e.g. a brush spring-biased into contact with the
electrically grounded roller 306) may be connected to the ground
310 and, via its engagement with the electrically grounded roller
306, may maintain the grounded roller 306 at a potential of 0V.
[0035] In one example the grounded roller 306 may comprise a
conductor. For example, an outer surface of the grounded roller 306
may comprise a conductor. The conductor may comprise a metal. In
one example the grounded roller may comprise a metallic outer
surface. In examples that utilise a rotatable coupling, a metallic
outer surface, or metallic part of the grounded roller 306, may be
in contact with the rotatable coupling so as to connect the
grounded roller 306 to the ground 310.
[0036] The apparatus 300 comprises a controller 308. The controller
308 is to apply an electric field between the developer roller 302
and the grounded roller 308. Therefore, in one example the
controller 308 is to apply an electric field in the vicinity of the
print media 304. In one example, the controller 308 is to apply an
electric field in the gap between the developer roller 302 and the
grounded roller 306.
[0037] In one example, the controller 308 is to apply an electric
field such that there is a negative potential in a region remote
from the substrate and/or the controller 308 is to apply an
electric field such that there is a negative potential in a region
proximate the developer roller. In this way, there will be a
potential difference between the developer roller 302 and the
grounded roller 306 which will cause ink from the developer roller
to migrate toward the grounded roller 306 whereupon it will be
deposited onto the print media 304 advancing between the rollers
302, 306. In one example the controller 308 is to control the
current supplied to a negative electrode to create the electrical
field and potential difference between the rollers 302, 306. In
this example the negative electrode may be proximate the developer
roller 302.
[0038] In one example, the controller 308 is to vary the strength
of the DC in proportion to the dielectric coefficient of the print
media, as print medias of different composition (e.g. comprising
plastic or paper) or of different thickness may comprise different
dielectric coefficients. In some examples the controller 308 may be
to measure the thickness of the print media 104 and adjust the
electric field based on the measured thickness. In other examples,
the controller 308 may comprise a memory, and the dielectric
coefficient of a particular print media 304 may be entered into the
controller 308 memory which (e.g. via a look-up table) may
associate a particular electric field strength so as to ensure
printing fluid migration toward the grounded roller 302 for that
print media 304. The strength of the electric field may therefore
be relative to the dielectric coefficient of the substrate.
[0039] The apparatus 300 may be to substantially cover the print
media 304 with ink. For example, the apparatus 300 may be to print
a background on a print media 304. In this way the apparatus 300
may be to "flood" the print media 304 with ink. For example, the
substrate 304 may be a paper or plastic substrate intended for use
with product packaging and the apparatus 100 may be to print a
background colour onto the substrate.
[0040] The apparatus 300 may comprise an engagement mechanism to
move the developer roller 302 relative to the grounded roller 306,
or the grounded roller 306 relative to the developer roller 302.
For example, the engagement mechanism may be to create a nip
between the two rollers 302, 306 for the print media 304 to advance
through.
[0041] In one example, the controller 308 may apply the electric
field between the rollers 302, 306 by supplying current to the
developer roller 302. In this example the controller 308 may be to
supply current so as to maintain the developer roller 302 at a
negative potential. For example, the developer roller 302 may be
connected to a source of DC and the controller 308 may be to
control the current supplied to the developer roller 302.
[0042] For example, the developer roller 302 may be in contact with
a rotatable coupling such as a bearing, bushing or brush, and the
rotatable coupling may be in contact with a source of DC, For
example, the DC source may supply current to the developer roller
302 via a rotatable coupling comprising a conductor. The conductor
may comprise a metal. For example, a bearing comprising a metallic
bearing housing may be connected to a conductor (e.g. copper wire
etc.) connected to a DC source, A rotatable bearing element within
the bearing housing may then transfer the current from the
conductor, through the bearing housing, to part of the developer
roller 302. The developer roller in one example may comprise a
semiconducting material. In another example, the developer roller
302 may be in contact (either directly or indirectly) with a source
of AC (in some examples, with a rectifier to convert the AC to
DC).
[0043] In one example, (e.g. in use) the electric field applied by
the controller 308 may create a potential difference, or voltage,
is created across the gap between the developer roller 302 and the
grounded roller 306. The air between the surfaces of the developer
roller 102 and grounded roller 106 may develop an electrical
conductivity. The apparatus 300 (e.g. under the control of a
controller, e.g. controller 308) may then advance the print media
304 in between the charged and grounded rollers 302, 306 (e.g
utilising the engagement mechanism to move them proximate one
another), and printing fluid such as ink may be transferred to the
developer roller 302, e.g. as described above. As printing fluid is
transferred to the developer roller 302, and the developer roller
302 rotates, the printing fluid on the surface of the developer
roller 302 will be rotated into proximity with the grounded roller
106, and rotated into proximity with the print media 304 advancing
in between the two rollers 302, 306. Due to the potential
difference resulting from the applied electric field in between the
two rollers 302, 306, printing fluid on the surface of the
developer roller 302 may be caused to migrate toward the grounded
roller 102 whereupon it will be deposited onto the surface of the
print media 104 advancing in between. The applied electric field
therefore facilitates the transfer of ink toward the substrate.
Therefore, the apparatus 300 deposits ink onto the surface of the
print media 104.
[0044] The printing fluid may therefore comprise conductive ink and
may, when placed in an electric field flow, towards a higher
potential. For example the printing fluid may comprise charged
particles and an applied electric field may cause the charged
particles to move towards a higher potential, for example the ink
may comprise negatively charged particles).
[0045] FIG. 4 shows an example method 400. The method 400 may be a
method of printing (or transferring or depositing) ink to a
substrate. The method 400 may be a method of printing a substrate,
or printing to a substrate. The method 400 may be a method of
substantially flooding a substrate with printing fluid. The method
400 may be a method of operating a printing apparatus.
[0046] The method 400 comprises, at block 402, operating a
developer roller to receive printing fluid. In one example, the
developer roller may be to transfer printing fluid to a substrate.
At block 404 the method 400 comprises advancing a substrate
proximate a guide roller, e.g. the guide roller may be to guide the
substrate. For example, block 404 may comprise operating a drive
unit to advance the substrate. At block 406 the method 400 may
comprise applying, by a controller, an electric field between the
guide roller and the developer roller. At block 408 the method 400
comprises varying, by a controller, the strength of the electric
field based on the dielectric coefficient of the substrate.
[0047] Therefore, a controller may be to apply an electric field
between the guide roller and the developer roller, and to vary the
applied electric field based on the dielectric coefficient of the
substrate, and blocks 406 and 408 of method 400 may comprise
operating the controller to apply and vary the electric field,
respectively. The guide roller may be a grounded roller, e.g, the
guide roller may be held at a potential of 0V. Block 404 of method
400, in one example, may comprise advancing the substrate between
the guide roller and the developer roller.
[0048] In one example the developer roller may be a charged roller
and the controller may be to supply current to maintain the
developer roller at a negative potential (in examples where the
guide roller is grounded). In this example block 406 may comprise
supplying a current to the developer roller and block 408 may
comprise varying that current. In another example the developer
roller and the guide roller may both be held at a positive
potential, the guide roller being at a higher potential, and the
controller may be to supply current to both rollers. In this
example block 406 may comprise supplying current to the developer
roller and the guide roller and block 408 may comprise varying that
current. Therefore, in one example the controller 408 may be to
supply current, or an electrical potential, to each one of the
developer rollers and the guide rollers. In this case each roller
operates as an electrode to create the potential difference
therebetween. In another example, applying the electric field
(block 406) may comprise applying a current, or an electrical
potential, to two electrodes, for example two plates each having a
different electrical potential.
[0049] FIG. 5 shows an example tangible (and non-transitory)
machine readable medium 500 in association with a processor 502.
The tangible machine readable medium 500 comprises instructions 504
which, when executed by the processor 502, cause the processor 502
to carry out a plurality of tasks. The instructions 504 comprises
instructions 506 to receive ink at a developer roller. The
instructions 504 comprises instructions 508 to apply an electric
field in the region of the developer roller. The instructions 504
comprises instructions 510 to Advance a substrate proximate the
developer roller. The instructions 504 comprises instructions 512
vary the strength of the electric field based on a dielectric
coefficient of the substrate.
[0050] In one example, the instructions 504 comprise instructions
to advance the substrate in between the developer roller and an
electrically grounded roller. In one example the instructions 504
comprise instructions to maintain the grounded roller at 0V.
[0051] In one example, the instructions 504 comprise instructions
to supply current to the developer roller to create a potential
difference between the developer roller and a region proximate the
substrate.
[0052] In one example, the instructions 504 comprise instructions
to supply a first current to the developer roller and a second
current to a second, guide, roller (e.g. proximate the substrate)
to thereby create (in one example, maintain) a potential difference
between the developer and guide rollers.
[0053] Examples in the present disclosure can be provided as
methods, systems or machine readable instructions, such as any
combination of software, hardware, firmware or the like. Such
machine readable instructions may be included on a computer
readable storage medium (including but is not limited to disc
storage, CD-ROM, optical storage, etc.) having computer readable
program codes therein or thereon.
[0054] The present disclosure is described with reference to flow
charts and/or block diagrams of the method, devices and systems
according to examples of the present disclosure. Although the flow
diagrams described above show a specific order of execution, the
order of execution may differ from that which is depicted. Blocks
described in relation to one flow chart may be combined with those
of another flow chart. It shall be understood that each flow and/or
block in the flow charts and/or block diagrams, as well as
combinations of the flows and/or diagrams in the flow charts and/or
block diagrams can be realized by machine readable
instructions.
[0055] The machine readable instructions may, for example, be
executed by a general purpose computer, a special purpose computer,
an embedded processor or processors of other programmable data
processing devices to realize the functions described in the
description and diagrams. In particular, a processor or processing
apparatus may execute the machine readable instructions. Thus
functional modules of the apparatus and devices may be implemented
by a processor executing machine readable instructions stored in a
memory, or a processor operating in accordance with instructions
embedded in logic circuitry. The term `processor` is to be
interpreted broadly to include a CPU, processing unit, ASIC, logic
unit, or programmable gate array etc. The methods and functional
modules may all be performed by a single processor or divided
amongst several processors.
[0056] Such machine readable instructions may also be stored in a
computer readable storage that ca guide the computer or other
programmable data processing devices to operate in a specific
mode.
[0057] Such machine readable instructions may also be loaded onto a
computer or other programmable data processing devices, so that the
computer or other programmable data processing devices perform a
series of operations to produce computer-implemented processing,
thus the instructions executed on the computer or other
programmable devices realize functions specified by flow(s) in the
flow charts and/or block(s) in the block diagrams.
[0058] Further, the teachings herein may be implemented in the form
of a computer software product, the computer software product being
stored in a storage medium and comprising a plurality of
instructions for making a computer device implement the methods
recited in the examples of the present disclosure.
[0059] While the method, apparatus and related aspects have been
described with reference to certain examples, various
modifications, changes, omissions, and substitutions can be made
without departing from the spirit of the present disclosure. It is
intended, therefore, that the method, apparatus and related aspects
be limited only by the scope of the following claims and their
equivalents. It should be noted that the above-mentioned examples
illustrate rather than limit what is described herein, and that
those skilled in the art will be able to design many alternative
implementations without departing from the scope of the appended
claims.
[0060] The word "comprising" does not exclude the presence of
elements other than those listed in a claim, "a" or "an" does not
exclude a plurality, and a single processor or other unit may
fulfil the functions of several units recited in the claims.
[0061] The features of any dependent claim may be combined with the
features of any of the independent claims or other dependent
claims.
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